Question

I am trying to manually create the signature tag for a web service call. I accessed the certificate from the keystore and accessed the public key for the certificate. I now have the problem in converting the RSAKeyValue to ds:CryptoBinary type. Code returns the Biginteger value for mudulus and exponent and I am looking for a method or algorithm to convert them to octets and then converting to Bas64. Here is my code

RSAPublicKey rsaKey  = (RSAPublicKey)certificate.getPublicKey();
customSignature.Modulus = rsaKey.getModulus(); 
customSignature.Exponent = rsaKey.getPublicExponent();

Is there any solution available in Java for converting the integers to octet representation?

Answer 1

Try following code using apache commons codec framework:

BigInteger modulus = rsaKey.getModulus();
org.apache.commons.codec.binary.Base64.encodeBase64String(modulus.toByteArray());